diff --git a/litellm/llms/vertex_ai/gemini/transformation.py b/litellm/llms/vertex_ai/gemini/transformation.py
index 9afa5dec4658..fa20386da79e 100644
--- a/litellm/llms/vertex_ai/gemini/transformation.py
+++ b/litellm/llms/vertex_ai/gemini/transformation.py
@@ -351,15 +351,28 @@ def _gemini_convert_messages_with_history(  # noqa: PLR0915
                             img_element = element
                             format: Optional[str] = None
                             media_resolution_enum: Optional[Dict[str, str]] = None
-                            if isinstance(img_element["image_url"], dict):
-                                image_url = img_element["image_url"]["url"]
-                                format = img_element["image_url"].get("format")
-                                detail = img_element["image_url"].get("detail")
+                            raw_image_url = img_element.get("image_url")
+                            if raw_image_url is None:
+                                raise litellm.BadRequestError(
+                                    message="Invalid message content: element type is 'image_url' but 'image_url' field is missing ",
+                                    model=model,
+                                    llm_provider="vertex_ai",
+                                )
+                            if isinstance(raw_image_url, dict):
+                                image_url = raw_image_url.get("url")
+                                if image_url is None:
+                                    raise litellm.BadRequestError(
+                                        message="Invalid message content: element type is 'image_url' but 'url' field is missing inside 'image_url' ",
+                                        model=model,
+                                        llm_provider="vertex_ai",
+                                    )
+                                format = raw_image_url.get("format")
+                                detail = raw_image_url.get("detail")
                                 media_resolution_enum = (
                                     _convert_detail_to_media_resolution_enum(detail)
                                 )
                             else:
-                                image_url = img_element["image_url"]
+                                image_url = raw_image_url
                             _part = _process_gemini_media(
                                 image_url=image_url,
                                 format=format,
diff --git a/tests/test_litellm/llms/vertex_ai/gemini/test_gemini_image_url_missing_field.py b/tests/test_litellm/llms/vertex_ai/gemini/test_gemini_image_url_missing_field.py
new file mode 100644
index 000000000000..10fc68ecaad6
--- /dev/null
+++ b/tests/test_litellm/llms/vertex_ai/gemini/test_gemini_image_url_missing_field.py
@@ -0,0 +1,52 @@
+import pytest
+from typing import List, cast
+
+import litellm
+from litellm.llms.vertex_ai.gemini.transformation import (
+    _gemini_convert_messages_with_history,
+)
+from litellm.types.llms.openai import AllMessageValues
+
+
+def test_missing_image_url_field_raises_bad_request_error():
+    """When element type is 'image_url' but 'image_url' field is missing, a BadRequestError is raised."""
+    messages = cast(
+        List[AllMessageValues],
+        [{"role": "user", "content": [{"type": "image_url"}]}],
+    )
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        _gemini_convert_messages_with_history(messages, model="gemini-1.5-pro")
+    assert "'image_url' field is missing" in str(exc_info.value)
+
+
+def test_missing_url_inside_image_url_dict_raises_bad_request_error():
+    """When image_url is a dict but 'url' key is absent, a BadRequestError is raised."""
+    messages = cast(
+        List[AllMessageValues],
+        [{"role": "user", "content": [{"type": "image_url", "image_url": {"detail": "high"}}]}],
+    )
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        _gemini_convert_messages_with_history(messages, model="gemini-1.5-pro")
+    assert "'url' field is missing inside" in str(exc_info.value)
+
+
+def test_explicit_null_image_url_raises_bad_request_error():
+    """When image_url key is present but explicitly null, a BadRequestError is raised."""
+    messages = cast(
+        List[AllMessageValues],
+        [{"role": "user", "content": [{"type": "image_url", "image_url": None}]}],
+    )
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        _gemini_convert_messages_with_history(messages, model="gemini-1.5-pro")
+    assert "'image_url' field is missing" in str(exc_info.value)
+
+
+def test_empty_dict_image_url_raises_bad_request_error():
+    """When image_url is an empty dict (no url), a BadRequestError is raised."""
+    messages = cast(
+        List[AllMessageValues],
+        [{"role": "user", "content": [{"type": "image_url", "image_url": {}}]}],
+    )
+    with pytest.raises(litellm.BadRequestError) as exc_info:
+        _gemini_convert_messages_with_history(messages, model="gemini-1.5-pro")
+    assert "'url' field is missing inside" in str(exc_info.value)